Effects of Hand and Foot Heating on Diver Thermal Balance.

Divers at rest immersed in cold water for long durations wearing passive thermal protection garments are limited by low finger and toe temperatures, which cause pain and numbness before rectal temperatures fall to unsafe levels. It was reasoned that low levels of hand and foot heating might improve diver comfort. Supplemental heating of the hands and feet to maintain finger and toe temperatures between 12 and 18 C (after passive cooling) was employed. A total of 32 divers wearing a dry suit with M-600 Thinsulated undergarments were immersed for periods of up to 8 hours in 3 C water. The divers wore electrical resistance heated gloves and socks over polypropylene liners and under Thinsulated insulation, or warm-water-perfused gloves and socks over polypropylene liners and under foam neoprene insulation. Hands and feet remained dry by communication with the dry suit. Water perfusion rate or electrical power was adjusted to maintain desired digit temperatures. Supplemental heating did not reduce the need for adequate passive whole body thermal insulation for long-duration immersions in cold water. Supplemental heating did reduce hand and foot discomfort at low energy cost, and reduced the decrement in manual dexterity compared to no heating. The low energy cost of resistance heating makes this feasible for immediate use by the Fleet. Keywords: Diving suits; Low temperature; Fingers/feet; Heat balance; Thermal insulation/ underwear; Temperature control; Stress physiology.

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